1. Field of the Invention
This invention relates generally to a system and process for the agglomeration of carbonaceous particles and, in particular, it relates to the agglomeration of coal and coke fines, collected in cyclones, bag houses and other particle separation systems, in a slurried medium. The present invention further relates to the agglomeration of potential fugitive carbonaceous dust in process/mining and transportation environment through application a spray. The system of additives described herein, mixed in varying proportions, can be used for the above and related applications for recovery, suppression and utilization of carbonaceous fines and dust.
2. Description of the Prior Art
Coal dust is a generally unwanted but inevitable fact of life in most phases of coal utilization technology. It is known that powdered coal, i.e., coal dust, is produced in great quantities during mining of coal, during its handling before and after shipment, and during shipment and storage. The coal powder is the result of the mechanical effects of mining and grinding processes. Similarly, the transport or handling of coal has the effect of inducing contact between large pieces of coal and results in the creation of fines. Coal powder is also due to weathering and oxidation of stored coal.
The formation of powdered coal leads to several significant problems. Powdered coal can lead to environmental disturbances, including both threats to health and vegetation and aesthetic damage. Powdered coal can permeate the air of mining sites or other work sites and is highly flammable and explosive. An additional problem is that when powdered coal cannot be used, its economic value and energy value is totally lost. For these and other reasons, systems for collecting and reducing the dispersal of coal dust must be used.
In the past, the principal means relied on for abatement of fugitive dust from manufacturing facilities are cyclones, electrostatic precipitators, fabric filters, and scrubbing. Because of the high collection efficiency, bag houses are used in many shipping mines. The bags are then shaken down and the coal dust is placed on conveyors to be loaded into railroad cars for shipping. Because of danger of spontaneous combustion, as little coal dust as possible is stored or stockpiled over long periods of time.
A particularly difficult dust problem arises out of the handling of calcined coke. Since the particulate calcined coke is fragile, its movement generates calcined coke dust that is collected through an air/recovery bag house system. When the bag house dumps the collected calcined coke dust, it is discharged either to a waste container or back onto the coke being transported that compounds the dust load. The disposal is difficult, cumbersome, and wasteful of an otherwise useful product whereas return of collected dust increases the likelihood of its release to the outside atmosphere.
In the following, distinction is made between:
the carbonaceousxe2x80x94coal, char, and cokexe2x80x94particles collected in particle separation devices described earlier; this is hereafter referred to as Case A
the carbonaceousxe2x80x94coal, char and cokexe2x80x94dust, for example in process/mining environment, which has the potential to become air-borne during loading/unloading, transportation on conveyor belts or otherwise; this is hereafter referred to as Case B.
In the past, in order to reduce the problem of coke and coal fines with reference to Case A, a variety of methods have been proposed. These prior methods are primarily off-line methods. Processes are known where coal fines are subjected to various conditions, typically high heats and/or pressure, and then mechanically compressed or formed into pellets or briquettes. Unfortunately, these processes have energy and equipment requirements that make them unattractive and expensive for most coal dust reduction applications.
A variety of methods used for producing compact coal dusts such as pellets or briquettes from coal fines involve the use of binders such as sulfite lye, urea-formaldehyde resins, phenol-formaldehyde resole resins, polyvinyl alcohol, or bitumen. However, these known processes have disadvantages. The addition of inorganic material tends to increase the ash content of the coal fines compact thus reducing the fuel value of the coal. In addition, many organic binders make the coal fins/binder mixture sticky and difficult to handle. Furthermore, the organic substances used are expensive and require particular precautions during handling.
In the case of coke dust production, the use of aqueous asphalt emulsion and surface-active agents has been proposed. Unfortunately, none of these dust control references offer a suitable solution for the recovery of coke dust. Perhaps this inadequacy is because the coke dust is neither mineral nor coal, both by definition and wetting characteristics.
As regards to Case Bxe2x80x94essentially an on-line dust mitigation strategyxe2x80x94a variety of chemical mixtures, applied in the form of a spray, have been used in the past. Many of these conventional methods employ comparatively expensive chemicals. According to practitioners, the efficacy of the agglomerating mixtures is short-lived in many cases. The stability, under the wide range of ambient temperature conditions encountered in practice, has also been somewhat limited.
Therefore, a need exists for a low-cost method for the recovery and handling of coal finesxe2x80x94for Case A as well as Case B. Additionally, there exists a need for a system and process for agglomerating coal, coke, and more general, carbonaceous matter fines as generated from many different sources. Further, a need exists for a system of providing additives, mixed in varying proportions, for use in the recovery, suppression, and utilization of carbonaceous fines and dust in process/mining/transportation environments. Still further, there exists a need for a process having significant economic advantages over past attempts in the field in that little energy input is required and much of the process chemistry is recycled.
The present invention is method for agglomerating and processing carbonaceous fines is provided. The process comprises powdering the carbonaceous fines, mixing the powdered carbonaceous fines with an organic liquid creating a slurry, adding a predetermined amount of an aqueous electrolyte to the slurry creating agglomerated particles, settling the large agglomerated particles resulting in a settled mixture of agglomerated coal fines and reagent liquor, and separating the agglomerated coal fines from the reagent liquor.
The present invention further includes a system for agglomerating and processing carbonaceous. The system comprises means for powdering the carbonaceous fines. A mixing apparatus mixes the powdered carbonaceous fines with an organic liquid with the mixed powdered carbonaceous fines and organic liquid creating a slurry. Means are provided for adding a predetermined amount of an aqueous electrolyte to the slurry creating agglomerated particles. A settler apparatus settles the large agglomerated particles resulting in a settled mixture of agglomerated coal fines and reagent liquor. Means are provided for separating the agglomerated coal fines from the reagent liquor.